Human Respiratory System: Mechanisms, parts etc..

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human respiratory system

Respiratory System in Human

Respiratory system in humans, which consumes oxygen and expels carbon dioxide. The deoxygenated blood collects carbon dioxide and other waste products and moves them back to the lungs, where they are pumped out of the body when we breathe out. These include the nose, pharynx, larynx, trachea, bronchi, and lungs.

Exchange of gases

During breathing the oxygen reach air these are the alveoli and that is where the exchange starts and exchange of gases takes place in two-level so classified as

  1. pulmonary exchange (external gases exchange)
  2. tissue level exchange (internal gases exchange)

first of all we need to understand the term partial pressure (pp):

Partial pressure is defined as the pressure exchanged by a gas in a mixture of gases irrespective of the concentration of other gases.

pulmonary exchange (external gases exchange)

This is also known as a pulmonary exchange respiratory system. In this exchange, the Gases exchange is happening in the lungs.

Oxygen uptake that is happening by the parliamentary blood.

In the alveolar air or the air that is rushing into through the nostrils into the alveoli. Here, the partial pressure of oxygen is about 104, MMR mercury whereas, in the venous blood, the partial pressure of oxygen is about 40 mm of mercury. So, here we can find the difference of the partial pressure is about 64 mm of mercury.

Now, because of this difference, because of the process of simple diffusion, because of the gradient in this partial pressure of oxygen, what happens the oxygen it rushes into the blood Right. So after the diffusion, the partial pressure of oxygen raises into about 95 mm of mercury in the venous blood.

Carbon dioxide uptake by the alveolar air.

In the lungs of respiratory system, the partial pressure of carbon dioxide in the pulmonary capillaries is about 46, MMR Mercury, whereas in the alveolar air, the carbon the partial pressure of carbon dioxide is about 40 mm of mercury.

So, we can see there is a difference about 6 mm of mercury, because of this partial pressure of partial pressure difference, which is about 6 mm of mercury, what happens it results in a diffusion of carbon dioxide from the blood into the alveolar A.

So, after the diffusion of the partial pressure of carbon dioxide in the pulmonary capillary, it decreases to about 14 mo mercury. So, this was the patch exchange in which that is happening in the lungs.

Tissue level exchange (internal gases exchange)

This is also known as tissue level respiratory system. The exchange that is happening in the tissues.

Uptake of oxygen by tissue

we have discussed that the blood has been oxygenated well, while it has traveled into the lungs.

Now, the partial pressure of oxygen in this oxygenated blood has raised to about 95 mm of marketing.

So, this blood reaches each and every cells and tissues of our body, whereas, the partial pressure in the interstitial fluid that is inside the cells is about 20 mm of mercury, right.

So, we can see there is a huge difference because of this huge difference in the partial pressure of oxygen from the blood oxygen easily diffuses into the cells or the interstitial fluid.

The rapid diffusion of oxygen into the tissues happen and because of this, the partial pressure of oxygen now falls back to 40, MMR mercury.

Carbon dioxide uptake by the tissues.

In human respiratory system, The partial pressure of carbon dioxide in the tissues is About 45 to 60, mmf Mercury, whereas in the arterial blood which has been oxygenated from the alveoli, the partial pressure of carbon dioxide is about 14 m of mercury.

So you can see there’s a quite a high amount of difference of carbon dioxide partial pressure, because of this, there is rapid diffusion of carbon dioxide from the body to the capillaries. And we have also discussed that the carbon dioxide has 2520 to 25 times more solubility in the blood than as compared to that of the oxygen.

So partial pressure of oxygen-carbon dioxide here in the blood, it increases to about 46 mm of mercury. So in this way, this process of exchange of carbon dioxide and oxygen happens in the lungs and in the tissues

Steps involved in respiration –

(i) Breathing or pulmonary inhalation
(ii) Spread of gases (O2 and CO2 ) across the alveolar membrane.
(iii) Transportation of gases by the blood
(iv) Distribution of O2 and CO2 between blood and tissues.
(v) The utilization of O2 by the cells for catabolic reactions and resultant discharge of CO2.

Parts of the Respiratory System of Human

the respiratory system in human includes your,

respiratory System in Human with diagram and parts
Parts of the Respiratory System

Nose and nasal cavity

The first organ of respiratory system is nose or nosal cavity. The nasal cavity is the inside of the nose. The nasal cavity is the upper part of the respiratory system and provides the nasal passage for inhaled air from the nostrils to the nasopharynx and the rest of the respiratory tract. The paranasal sinuses surround and drain into the nasal cavity.


Your sinuses are air spaces in your skull and facial bones that make up the upper piece of your respiratory tract from your nose into your throat. A sinus is a sac or pit in any organ or tissue, or an irregular depression or entry brought about by the annihilation of tissue Mouth.

Throat (pharynx)

The pharynx is the part of the throat behind the mouth and nasal cavity. It about a cone-shaped passageway. It contains three sections they are nasopharynx, oropharynx, and laryngopharynx.

Voice box (larynx)

The larynx is commonly called the voice box or glottis this is the passageway for air between the pharynx and the trachea below. This is a 2 inch long tube-shaped organ in the neck. It is used inbreathe, talk, or swallow. Its outer wall of cartilage forms the area of the front of the neck referred to as the “Adam’s apple.”The vocal cords are two bands of muscle that form a “V” inside the larynx.

Windpipe (trachea)

In other words, the trachea is known windpipe. it is around 4 inches in length and not exactly an inch in distance across.

That starts simply under the larynx (voice box) and runs down behind the breastbone (sternum). The trachea isolates into two little cylinders called bronchi, one bronchus for each lung.

The trachea is made out of around 20 rings of the intense ligament. The back piece of each ring is made of muscle and connective tissue. Clammy, smooth tissue called mucosa lines within the trachea.

The trachea broadens and protracts somewhat with every breath in, coming back to its resting size with every breath out.


The muscles of the diaphragm starts from the lower part of the sternum (breastbone). the lower six bones and the lumbar vertebrae of the spine attached to a central membranous tendon. The contraction of diaphragm increases the internal height of the thoracic cavity.


In Human respiration system, the lung are two soft spongy and cone-shaped structures present in thoracic cavity on either side of the heart that includes the respiratory system in human. They extend from the base of the neck to the diaphragm.  The trachea (windpipe) conducts inhaled air into the lungs through its tubular branches, called bronchi. 

Diagrammatic representation of exchange of gases at the alveolus and
the body tissues with blood and transport of oxygen and carbon dioxide
Diagrammatic representation of exchange of gases at the alveolus and
the body tissues with blood and transport of oxygen and carbon dioxide(respiratory system)

Bronchial tubes/bronchi

In Human, air goes into trachea (windpipe) through the nose or mouth. Then, that air passes through the bronchial tubes, into the lungs and finally back out again. The bronchial tubes, which branch into smaller tubes called bronchioles or bronchi .

Air sacs (alveoli)

Alveoli located at the end of bronchial tube. In a human body, their are 480 million alveolis are present. Alveoli are tiny air sacs in the lungs that take up the oxygen and keep the body going. Alveoli are microscopic in nature.


Capillaries are very tiny blood vessels contain a single red blood cell can barely fit through them. The capillaries are exchanged the oxygen, nutrients, and wastes between the blood and the tissues.

The respiratory system in human consists of all the organs involved in breathing. These include the nose, pharynx, larynx, trachea, bronchi, and lungs. … The nose, pharynx, larynx, trachea and bronchi all work like a system of pipes through which the air is funneled down into our lungs.

Respiratory system RAQ

What is respiration ?

In living organisms, respiration involves the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances.

What is respiration considered as exothermic reaction ?

Respiration is an exothermic process because in respiration the carbon dioxide present in food breaks down to form glucose. This glucose combines with the oxygen in the cells of our body and releases a large amount of energy.

What is aerobic respiration ?

Aerobic respiration is the process of producing cellular energy that involves oxygen. such as fats and sugars, for energy.

What is anaerobic respiration ?

Anaerobic respiration is the process of producing fats and sugars etc, for energy without using oxygen.

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